The formation of a neat, secure and practically invisible seam or splice between two sections or rolls of modern-day wide gage carpet has been a formidable problem for quite some time in the industry. The older method for seaming carpet sections with a lap seam causes two joined carpet edges to protrude at about 90.degree. from the carpet plane, and in addition to being unsightly causes difficulties in a shearing machine in that the machine must be stopped and its blades elevated so that the spliced carpet may be advanced with its protruding seam beyond the shearing blades. The customary lap seam causes at least a 12 inch waste strip on a 15 foot wide carpet roll, and a similar wastage will occur with the carpet printing operation. The carpet industry for a long time has wasted thousands of dollars daily because of the customary lap seaming of carpeting.
In awareness of the above industry problem, some prior art proposals have been brought forth with the objective of forming butt seams between carpet edges which require joining and some examples of the known patented prior art for this purpose are contained in U.S. Pat. Nos. 2,655,885 and 3,440,981. So-called railway sewing machines of more general utility are also known in the prior art.
In general, the prior art proposals for producing butt seams or splices between carpet sections have not been entirely satisfactory and practical for several reasons. Among these reasons is the inability of conventional sewing machines to handle the large thicknesses of modern-day pile carpeting where two superposed sections to be joined will measure up to 2 inches in thickness. Also, the prior art machines customarily can handle only a single thickness or gage of much less than the above-specified total thickness which the machine of the present invention can easily handle. In the invention, a novel presser foot and throat plate structure is provided to deal with this thickness problem and works with great efficiency.
More importantly, the prior art machines seem to be incapable through their stitch-forming mechanisms to consistently form a butt seam with precisely the required slack in the stitches to eliminate gapping between the two carpet sections or overlapping the buckling at the seam as when insufficient slack is present in the stitching. By means of an improved and very efficient sewing head involving a novel looper arrangement, and increased sewing needle stroke, the machine of the invention has been enabled to form consistently and reliably an ideal butt seam or splice between wide carpet sections which is almost perfectly uniform across the full width of wide gage carpet, up to fifteen feet and more. More particularly, a novel extension finger on one of the two loopers of the stitch-forming mechanism assures the formation of precisely the proper amount of slack in the thread from which the butt seam stitches are formed, thus enabling the two joined carpet sections to "butt out" in the desired manner after formation of the seam and the unfolding of the two carpet sections into a common plane. The butt seam produced by means of the invention can be made virtually invisible and certainly far superior in appearance as well as durability and consistency to anything heretofore known in the industry.
Another very important improvement feature over the prior art in the present machine is the pivotal mounting of the sewing machine or head and the powered carpet trimmer immediately in advance of the sewing head on the carriage which supports both. This pivotal mounting of sewing machine and trimmer on right angular pivot axes enables a mechanic to easily gain access to the sewing head for making repairs without the necessity for removing the machine from the carriage or railway bed. This represents another significant saving of labor and time.
Still another important feature of the invention resides in the mated arrangement of the power trimmer and sewing machine on the common carriage in such a way that the trimmer produces a perfectly straight edge on the carpet sections immediately ahead of the stitching operation, with the scrap trimmings falling to the floor prior to the entry of the carpet sections into the stitch forming mechanism. Carpet scrap or waste is reduced to the absolute minimum by means of the invention.
Another significant feature of the invention resides in the use of an electric clutch between the driving sprocket for the carriage and the gear speed reducer coupled with the sewing machine drive motor. By this arrangement, the clutch will be energized only when the electric drive motor is energized so as to propel the carriage carrying the sewing machine and trimmer along the railway bed through the engagement of the carriage drive sprocket and a fixed length of sprocket chain which spans the railway bed lengthwise. When the sewing machine motor is off, the electric clutch becomes inactive and thus allows the carriage to be wheeled manually anywhere along the track of the railway frame, the drive sprocket for the carriage merely free-wheeling at this time.
Other important features and advantages of the invention will become apparent during the course of the following detailed description.